Glass softening range

A glass object can be used for indefinite periods below its annealing temperature but only for very short intermittent periods at the high end of its softening range. Fused silica is obviously very useful for high-temperature apparatus and Vycor, which contains a few percent of other oxides, is almost as good. At elevated temperatures fused quartz will devitrify, i.e., ciystallize and become opaque. 

Glass softens over a wide range of temperature. Ice melts at a precise temperature. Explain the difference. 

Fig. 2 Temperature-dependence of the modulus of elasticity (Young s modulus) of plastics (diagram). As an alternative to this modulus, tension a can also be plotted against constant elongation e or viscosity i), or other properties [2]. MSRe x,d- main softening range of elastomers, thermoplastics, duroplastics, Tgt associated glass transition temperature, Tfi flow point of the amorphous thermoplastic, //////// application range, application range...

Table 5.3 Glass transition temperature and softening range of polymers...

Fig. 3A-3 Definition of the glass transition temperature Tg by a diagram of length versus temperature during a measurement, as the intersection of the tangents to the elastic region B and to the liquid region to the right of C. In the Uansformation range C, the glass softens...

Sharanov, Yu. A. Effect of annealing polymer glasses on the temperature dependence of the heat capacity in the softening range. Vysokomolekul. Soedin. 

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